The invention relates to pelvic floor strength, and in particular an apparatus and method for qualitative assessment of pelvic floor muscular strength.
Pelvic floor weakness is a critical factor in the development of such dysfunctions like stress urinary incontinence, genital prolapse, and fecal incontinence. Accurate pelvic floor functional assessment is important when determining the degree of dysfunction, the amenability of the dysfunction to non-surgical therapy, and for monitoring the success of treatment. Multiple methods of pelvic floor strength assessment have been developed. Worth, Dougherty and McKey, Nurs. Res., 1986:35 and Brink et al., Nurs. Res., 1989:38 describe a method using digital pelvic assessment (DPA) scales; Bo and Kerschan-Schindl et al, Neurourol. Urodyn., 1992: and 2002:21, respectively, describe a method using vaginal pressure measurements; Jonasson et al., Acta Obstet. Gynecol. Scand. 1989:68 and Contreras and Coya, Int. Urogynecol J. 1996:7 describe the use of vaginal cones; Weidner, Barber et al, and Weidner, Sanders et al, Am. J. Obstet. Gynecol., 2000:183, respectively, describe the use of electromyographic activity measurement (EMG). However, Worth et al, Bo, Hahn et al., Gynecol. Obstet. Invest. 1996:41, Peschers et al. Int. Urogynecol. J. 2001:12 and Bo and Finckenhagen, Acta Obstet. Gynecol. Scand. 2001:80 have shown these methods to have disadvantages, such as subjective and indirect measurement, cumbersome data collection, measurement artifacts, or prohibitive cost for routine office use. In addition, the DPA is not designed to assess resting pelvic tone. Because it is the dynamic action of the muscles that is believed to prevent dysfunction, any static state measure may be a poor representation and of limited clinical utility.
Accurate assessment of pelvic floor muscle function has remained difficult to achieve. Previously described techniques have been limited by providing only indirect and subjective information on pelvic contractions in the form of generated vaginal pressure. The exceptions may be an instrumented vaginal speculum force gauge developed at the University of Michigan by Sampselle et al., Obstet. Gynecol. 1998:91 that is not commercially available and vaginal cones. However, the speculum also measures circumferential pressure, not retentive force.
Kerschan-Schindl et al. and Hahn et al. have shown pressure perineometry, a widely used technique, to be a reproducible method of measuring vaginal pressure in both continent and incontinent women. However, this instrument is limited in that it measures all pressure changes in the vagina. Contraction of the rectus abdominus and/or adductor muscles, in addition to the pelvic floor muscles, will result in increased pressure recordings. Further, most electronic pressure devices have a narrow sensor area, making placement a problem.
Perineometry using EMG activity is another commonly used method. Again, this method is limited because it is indirect and the origin of the potentials generated cannot be localized to the pelvic floor muscles. Previous studies by Peschers et al. demonstrated that adductor muscle activity increases EMG recordings. Additionally, surface EMG recording is inaccurate in quantitatively assessing muscular strength. Its usefulness maybe limited to biofeedback.
Kato and Kondo, Int. Urogynecol. J. 1997:8; Peattie et al., Brit. J. Obstet Gynaecol., 1988:95; and Wilson and Borland, Aust. N Z J. Obstet. Gynaecol. 1990: 30 showed weighted vaginal cones have also been useful in the assessment and rehabilitation of the pelvic floor. However, Bo, Acta. Obstet. Gynecol. Scand. 1995:74 showed that the cones are often not well accepted and are poorly correlated with physical findings and other pelvic assessment techniques. Hahn et al. demonstrated that women with severe prolapse or incontinence, reduced vaginal tone causes the cones to change position and allows retention in the posterior pelvis without the assistance of the pelvic floor muscles. Contreras Ortiz and colleagues reported on pelvic floor assessment using a modified weighted vaginal cone (the IVD test). The cones were larger than previously used cones, but the same shortcomings were suspected.
Another proposed method for pelvic floor functional assessment is ultrasound of the perineum to measure elevation of the bladder neck during a pelvic contraction. Reddy et al., Am. J. Obstet. Gynecol. 2001:185 showed this method to be useful as a biofeedback device because it discriminates between straining and a contraction; however, quantification of the strength of the pelvic floor contraction is not a possibility.
Finally, the least expensive method to assess pelvic floor muscular strength is digital palpation. Worth et al. and Brink et al. devised numerous scales, which have been shown to have good intra- and inter-observer reliability. This method, however, is limited because it is an indirect measurement of pressure, although some scales have attempted to overcome this shortcoming by including perineal lift as part of the assessment. It is also subjective, which has restricted its usefulness. Nonetheless, the speed and ease of use distinguish it between other currently accepted methods and are the reasons it was used for comparison in this study.
The use of spherical intravaginal devices to enhance pelvic floor rehabilitation in the management of genital prolapse has been previously reported by Adamkiewicz et al., Int. Urogynecol J. 2001:12 and Martin et al, Zentralbl. Gynakol. 1994:16 and is also known from the U.S. patent application Ser. No. 09/303,981. The device is conveniently a plastic sphere with a silicon thread attached for easy insertion and removal and is available in 28 –44 mm diameter sizes. Women perform pelvic floor exercises with the sphere in the vagina above the level of the levator ani. As the pelvic floor muscles strengthen the likelihood of device expulsion decreases.